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Safety Precautions
General Guide Lines
1.
It is advisable to insert an isolation transformer in the AC
supply before servicing a hot chassis.
supply before servicing a hot chassis.
2.
When servicing, observe the original lead dress, espe-
cially the lead dress in the high voltage circuits.
If a short circuit is found, replace all parts which have
been overheated or damaged by the short circuit.
cially the lead dress in the high voltage circuits.
If a short circuit is found, replace all parts which have
been overheated or damaged by the short circuit.
3.
After servicing, see to it that all the protective devices
such as insulation barriers, insulation papers, shields,
and isolation R-C combinations, are properly installed.
such as insulation barriers, insulation papers, shields,
and isolation R-C combinations, are properly installed.
4.
When the receiver is not to be used for a long period of
time, unplug the power cord from the AC outlet.
time, unplug the power cord from the AC outlet.
5.
Potential, as high as 31.5kV, is present when this moni-
tor is in operation. Operation of the Projection Monitor
without the rear cover involves the danger of a shock
hazard from the power supply. Servicing should not be
attempted by anyone who is not thoroughly familiar with
the precautions necessary when working on high voltage
equipment. Always discharge the anode of the projec-
tion tube to the Projection Monitor chassis before han-
dling the tube.
tor is in operation. Operation of the Projection Monitor
without the rear cover involves the danger of a shock
hazard from the power supply. Servicing should not be
attempted by anyone who is not thoroughly familiar with
the precautions necessary when working on high voltage
equipment. Always discharge the anode of the projec-
tion tube to the Projection Monitor chassis before han-
dling the tube.
6.
After servicing make the following leakage current
checks to prevent the customer from being exposed to
shock hazards.
checks to prevent the customer from being exposed to
shock hazards.
Leakage Current Cold Check
1.
Unplug the AC cord and connect a jumper between the
two prongs on the plug.
two prongs on the plug.
2.
Turn on the Projection Monitor’s power switch.
3.
Measure the resistance value, with an ohmmeter,
between the jumpered AC plug and each exposed
metallic cabinet part on the projection monitor, such as
screw heads, connectors, control shafts, etc. When the
exposed metallic part has a return path to the chassis,
the reading should be between 4 M
between the jumpered AC plug and each exposed
metallic cabinet part on the projection monitor, such as
screw heads, connectors, control shafts, etc. When the
exposed metallic part has a return path to the chassis,
the reading should be between 4 M
and 20 M
.
When the exposed metal does not have a return path to
the chassis, the reading must be
the chassis, the reading must be
.
Leakage Current Hot Check (See Fig.1)
1.
Plug the AC cord directly into the AC outlet. Do not use
an isolation transformer for this check.
an isolation transformer for this check.
2.
Connect a 2k
, 10W resistor, in series with an exposed
metallic part on the projection monitor and an earth such
as a water pipe.
as a water pipe.
3.
Use an AC voltmeter, with high impedance type, to mea-
sure the potential across the resistor.
sure the potential across the resistor.
4.
Check each exposed metallic part, and measure the
voltage at each point.
voltage at each point.
5.
Reverse the AC plug in the AC outlet and repeat each of
the above measurements.
the above measurements.
6.
The potential at any point should not exceed 1.0V rms.
In case a measurement is outside of the limits specified,
there is a possibility of a shock hazard, and the projec-
tion monitor should be repaired and rechecked before it
is returned to the customer.
In case a measurement is outside of the limits specified,
there is a possibility of a shock hazard, and the projec-
tion monitor should be repaired and rechecked before it
is returned to the customer.
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Hot-Check Circuit
Fig. 1
AC Voltmeter
To
Instrument's
Exposed
Metallic Parts
Instrument's
Exposed
Metallic Parts
2k
, 10W
Water Pipe
( Earth )
( Earth )
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